Insulated electrical conductors



Jan. 10, 1956 E. w. DAszEwsKl 2,730,467

INSULATED ELECTRICAL coNDucToRs Filed Sept. 2l, 1954 States Patent O 2,730,467 INSULATED ELECTRICAL CONDUCTORS Edward IW, Daszewski, Scotia, N. Y., assignor to General Electric Company, a corporation of New York Applicationv September 21, 1954, Serial No. 457,477

" 3 claims. (erin- 232) (Ram-f (Omen),

Rg i R1 where Z is an alkylene radical, for instance, methylene, ethylene, propylene, isopropylene, butylene, etc., R1, Rz and R3 are the same `or different substituents selected from the class consisting of hydrogen, halogen, alkyl radicals, aryl radicals, and aralkyl radicals, and n is awhole number equal to from 1 to 3; (b) a complex epoxide resin comprising a polyether derivative of a polyhydric organic compound, e; g., a polyhydric alcohol yether in which-the said polyether derivative contains epoxy groups which, for brevity, will hereinafter be referred to` as van ethoxyline resin; (c) an aminoplast resin, for example, the condensation reaction product of a' urjea ,and an aldehyde, and (d) a suitable solvent.

u-I't, is generally known that-without any modification, th'oxylinetresins.ares1owfcuring and somewhat brittle, and-accordingly unsuitable for certain uses, for instance, as wire coating insulation. When either urea or melaminegr'esins are blended` with `et-lioxyline resins, faster curing timejisppbtained andthe solutions are vstable for longer periods'i-of time.' However, when combinations of vthese resin systems areevaluated by application to wire'or `otherconductoryalthough curing is rapid, the resulting lms are somewhat soft but exible. Attempts have been `made .to improve the abrasion resistance of urea-ethoxyline resin systems to the point satisfactory foruse as wire-coating compositions bythe addition of various phenol-aldehyde resin. None of the phenolic vresi-nsremployed gave a satisfactory wire coating composition with a urea-ethoxyline resin system.

`Itnow has been discovered that excellent coating compositions, particularly useful as wire insulation, can

. CH: fno; e on`+ opongan-jon, A (lJHs I O be prepared by blending with a urea-ethoxyline resin composition, compounds corresponding to (a) above, obtained by reacting an epihalogenohydrin corresponding to the general formula where R is a halogen-substituted aliphatic radical, for example, chloromethyl, chloroethyl, chloropropyl, bromoethyl, etc., with a composition comprising a compound corresponding to general formula HOCH CHQOH HzOH or with mixtures oforganic compounds corresponding to the general formula 'R2 I Rl V where M is a member selected from the class consisting of hydrogen, sodium, potassium, and barium, and R1, R2 and Ra, and n have the meanings given above and preferably, although not essentially, n is equal to 3.

The invention will be understood more readily from the following description 4when considered in connection with the accompanying drawing, in which the single ligure is a cross-sectional view of an electrical conductor provided with insulation in accordance with thisinvention.

Ethoxyline resins of the type employed in preparing the present compositions are described more fully in Castan vPatent 2,324,483, Castan Patent 2,444,333, British Patent 518,057, and British Patent 579,698. Essentially, these ethoxyline resins are based on the resinous product of reaction of an epihalogenohydrin, for lin-A stance, epichlorohydrin, and an aliphatic polyhydric alcohol, for example, glycerine or a phenol having-at least 2 phenolic-hydroxy groups, for example bis-(4-hydroxy phenyl) dimethyl methane. Furtherexamples of ethoxyline resins which may be employed in the practice of the present invention are disclosed in U. S. Patents 2,494,295, 2,500,600, and 2,511,913. By reference, the aforementioned patentsareintended to be part of the present description of the ethoxyline resin used and, for brevity, the ethoxyline resins will not be described other than that they contain more than one epoxide group, e. g., from l to 2 or more epoxide groups per molecule, and may be preparedby effecting reaction between a polyhydric phenol or alcohol, forexample, phenol, hydroquinone, resorcinol, glycerine, and condensation products of phenols with ketones, for instance, bis-(4-hydroxyphenyl) dimethyl methane with epichlorohydrin. For example, the reaction of epichlorohydrin with bis-(4-hydroxyphenyl) dimethyl methane may be formulated as follows: Y

alkali where n has an average value varying from 0 to about 7. Many of these ethoxyline resins are sold under the name of Epon resins by Shell Chemical Corporation or Araldite resins by the Ciba Company. Data on several of the Epon resins found eminently suitable for the purposes of the present invention are given in the table below:

Table I Approximate v Epoxlde M. P. Epon l\o Esterification Equivalent Equivalent C C.

IIN-34 22S-290 lg 20-28 105 10-45 Liquid 175 3T-403 190 l27-1i3 200 145-l5a 130 (l-76 Urea-aldehyde condensation reaction products found eminently suitable in preparing compositions of the present invention include urea-aldehyde condensates prepared by condensing urea with an aqueous solution of an aldehyde, for example, formaldehyde under controlled conditions of time, temperature and acidity, well known to the art. Examples of other urea-aldehyde condensates which may be employed include the reaction products of a urea with acetaldehyde, propionaldehyde, butyraldehyde, etc.

The starting polymethylol' phenyl derivatives employed in preparing the epihalogenohydrin-polymethylol phenyl reaction products used in formulating the resinous compositions of the invention correspond to the general formula (Ra) o-o (C H1011) whereM is a member selected from the class consisting of sodium, potassium, or barium, and R1, R2 and Rs are members selected from the class consisting of hydrogen, halogen, alkyl, aryl, and aralkyl radicals. These compounds, which hereinafter will be referred to as the .methylol phenyl derivative, may be prepared by effectn ing reaction between about 1.5 to 3 mols of formaldehyde, preferably from about 1.8 to 2.5 mols formaldehyde, per mol of the phenol derivative corresponding to general formula R2 l R1 where m is a value equal to from 0 to 2 and preferably m is 0 and R1, Rz and R3 have the meanings given above. The reaction is conducted at a temperature such that no resinous material is formed. This temperature has been found to range, for instance, from about 15 C. up to about 65 C., above which temperature undesirable side reactions may take place. The reaction is conducted in the presence of about' 1 mol of alkali or alkaline hydroxide as, for example, sodium hydroxide, potassium hydroxide, and barium hydroxide per mol of the phenol.

The extent of the reaction between the hydrin and the F methylol phenate will depend on the reactivity of the hydrin and the duration of the reaction, the products containing from 1 to 3 methylol groups. If it is" desired to obtain the-isolated salt of, for instance, the sodium or barium methylol phenate derivative, it can be precipitated by diluting or pouring the reaction mixture into a suitable water-miscible solvent and separating the salt'from the liquid by ltration, decantation or other suitable means.

After the preparation of the methylol metal phenates described above, the latter may then be caused to react with the epihalogenohydrin compound corresponding to the general formula R-CH-CHz \0/ where R is a halogenated aliphatic radical, for example, a chloromethyl radical. For each mol of metal phenate prepared as described above, there is employed at least one mol of the hydrin, for example, 1 mol of epichlorohydrin. If desired, more than one mol of the hydrin may be used per mol of the methylol phenate. Thus, from about l to 1.5 or more mols of the hydrin per mol of the metal phenate can be used. Reaction occurs preferentially with the -OM group on the phenyl nucleus, where M has the meaning given above but may also occur to some extent with the methylol groups. The latter reaction with the methylol groups takes place generally after the OM group has been satisfied and the phenolic groups blocked. From an economical point of view, it is advantageous to use reaction products produced from a mixture of the uni, bis, and tris-(hydroxyrnethyl) compounds where the tris-(hydroxymethyl) derivative is present preferably, though not essentially, in an amount, by weight of the mixture, of over 25% or more, for example, an amount over 50%. The invention is not limited to this percent of the tris-(hydroxymethyl) derivative since smaller (e. g., 10 to 40%) or larger percents (e. g., from 40 to 90%) of the total of the uniand bis- (hydroxymethyl) phenyl compounds corresponding to the general formula where M has the meaning given above, and n is an integer equal to from 1 to 2 inclusive, may also be used without departing from the scope of the invention.

The proportions of each component employed in' preparing the present compositions may be varied within certain limits. Generally, on a weight basis, the ethoxyline resin may be employed in an amount corresponding to from about 10 to about 17%, the urea-aldehyde condensate may be employed in amountsV corresponding to from about 7 to about 15%, and the epichlorohydrin derivative of polymethylol phenol may be used in an amount corresponding to from about 0.1 to about 7%. TheV remainder ofthe composition is composed of solvent. Advantageously, onv a weight` basis', the' preferred ranges arev from-about 12 to about 16% ethoxyline resin, from about 9 to about 11% urea-aldehyde resin, and from about 1 to about 4% of the epichlorohydrin derivative of polymethylol phenol.

Solvents found eminently suitable in preparing the wirecoating enamels of the invention include mixtures of a hydrocarbon, for example, an aromatic hydrocarbon, such as benzene, toluene, xylene, or any of the higher boiling aromatic hydrocarbons with an aliphatic ketone, such as methyl ethyl ketone, methyl propyl ketone, methyl iso' propyl ketone, methyl isobutyl ketone, etc. Similarly, mixtures of any one of the aforementioned aromatic hydrocarbons may be employed with diacetone alcohol to give excellent vehicles for the resin solids of the present compositions. Other examples of solvents which may be employed include mixtures of a phenolic body, such as cresol, xylenol, etc., with an aromatic hydrocarbon, such as benzene, toluene, xylene, or any of the highV ash or other solvent naphthas commonly used in making wire cnamels. Another excellent vehicle for the present com- Y tion mixture.

, limits.

positions is a mixture -of cresols as commonly found in crevsylic acid. Generally, the solvents may be employed in amounts corresponding to from about 60 to about 80%, by weight of the enamel, a preferred range being from about 70 to about 75%, by weight of the enamel.

The folowing examplesgare given by way of illustration and not by way of limitation. All parts and percentages are by weight.

Example 1 This example illustrates the preparation of epoxide resin in which the methylol phenate derivative was prepared in situ so as to give a mixture of methylol phenols, that is, a mixture in which the uni, bis, and tris(hy droxymethyl) phenyl derivatives were present. More particularly, 1.83 part water, 8.34 parts phenol, and 7.33 parts of 50%.aqueous sodium hydroxide were placed in a stainless steelkettle and the temperature of the mixture adjusted to 40 C. by means of heated circulating water through the jacketsurrounding the kettle. 14.4 parts of 37% aqueous formalin were added slowly during the next fifteen or twenty minutes and the mixture held at 40 C. with constant agitation for a period of thirty minutes, after all the formalin had been added. The resulting product was cooled to room temperature at around -28 C. and allowed to stand about fifteen hours. This product, which is identified as product A, was. drawn olf into a container. Thereafter, 9.48 parts ethanol and 9.48 parts epichlorohydrn were charged to the samekettle and the temperature adjusted to about 58-60 C. Product A was added to the kettle over a thirty-minute period, after which the mixture was reacted at 80 C. with stirring for one hour. The mixture was cooled to 50 C. and the ethanol removed by vacuum stripping. The product was cooled to C. and decanted by removing the water from the top of the reac- The cooled product had a pH of 9.7. 0.7 part of 37% aqueous HCl was added to the mixture and the product washed with water by agitation at 60 C. for thirty minutes, cooled `to20-25 C. and the water layer again decanted so as to give a product having a pH of 8.8. The product was again washed with water followed by l a small quantity of 37% aqueous HCl and the washing carried out with agitation at 60 C. for thirty minutes and thereafter cooled. The Water was decanted and at this point the product had a pH of 8.2. The product was then dehydrated-undera vacuum of 27" mercury to give 10.67 parts of an epoxide resin which comprised 57% of the theoretical amount. Analysis of the resin showed it to contain 21.9% methylol groups and an epoxide value of 0.26 rnilliequivalent per gram.

It will be apparent that instead of the epichlorohydrnemployed in the foregoing example, other hydrins corresponding to the general formula where R is a halogenated saturated aliphatic radical other than the chloromethyl radical in epichlorohydrn, for instance, chloroethyl, chloropropyl, etc., may be used without departing from the scope of the invention. In addition, instead of using the particular phenol of phenols described in the foregoing examples, other substituted phenols may be employed.

The molar ratio of the hydrin and the particular methylol phenate employed may also be varied within wide Thus, although it is preferable to employ at least the same number ofmols of hydrin, for example, epif chlorohydrin, as there are phenolic hydroxyl groups or f potential hydroxyl groups attached to the phenyl nucleus as, for example, the OM group on the benzene nucleus,

where M is, for instance, sodium, potassium, and barium,

it will be apparent that smaller molar l'cunts of the hydrin may also be used whereby it is possible to obtain derivatives of only some of the phenyl-bonded OM groups in admixture with unmodified methylol phenol and methylol phenates. f

The conditions of reaction for obtaining compound may also be varied. The reaction to form the methylol phenate may be carried out at temperatures ranging, for example, from about room temperature to as high as S0-65 C. As pointed out previously, temperatures in excess of C. show a decrease in the yield of the desired compounds, since at temperatures above 65 C. resiniiication of the methylol groups may begin to take place and increases rapidly as the temperature rises. However, reaction between the hydrin and the methylol phenate may be conducted at higher temperatures, for instance, as high as -100 C., preferably between 6080 C., without undue condensation of the methylol groups.

Example 2` This example illustrates a typical composition of the invention.

A resinous composition was prepared having the following formulation:

Per cent by weight Epon 1007 15.15 Urea-formaldehyde condensate 10.4 Epichlorohydrin derivative of polymethylol phenoL 2.15 Cresylic acid 72.3

Following the procedure described in' Example 2,*another resinous composition Wasprepared having the following ingredients:

` Percent by weight Epon' 1007 13.0

Urea-formaldehyde condensate 10.4

Epichlorohydrin derivative of polymethylol phenol 4.3

Cresylic acids 72.3 Example 4 A composition was prepared in accordance withthe method disclosed in Martin 2,579,330, assigned to the assignee of the present invention, comprising (l) 1allyl Oxy-2,4,6-tris-(hydroxymethyl)` benzene and (2) a cornpound having the general formula where n is 1 or 2. This mixture of allyl ethers of methylol phenols was employed in formulating the following composition: Y

Y Percent by weight Epon 1007 13.0 Urea-formaldehyde resin.. 10.4 Methylol phenol allyl ethers 4.3 Cresylic yacid 72.3

v The enameled electric conductors were prepared by The results tabulated above clearly show that the conidrawing clean wire, for example, clean copper wire, positions of the invention are eminently suitable as insuthrough a body of enamel, substantially in accordance lation material for electrical conductors. The abrasionY with the procedure outlined in Jackson et al. 2,307,588, resistance of the enainels containing the epichlorohydrin assigned to the assignee of the present invention. More derivative of the polymethylol phenol, although somewhat specitically, the wire was passed through a bath contaiulower than the one containing polyvinyl formal resin, is ing the wire enamel and thereafter the coated wire was still substantially above the minimum of thirty strokes subjected to heat by introducing it into an oven wherein required for polyvinyl formal resins. The properties of the'enamel was baked at the required temperature. The the two enamels containing the epichlorohydrin deriva- Coating was baked simultaneously with the annealing of l0 tive of poiymethylol phenol is substantially the same in the copper. The wire was drawn through the bath at every case, with the exception of the 1X, 30% stretch various speeds ranging from ten feet per minute to in the elongation and exibility test, indicating that this twenty feet per minute. The enamel was applied by property decreases with an increase in percentage of the dies to 0.0508 wire with a total insulation of approxiderivative employed in the composition. Heat aging of mately three mils being obtained. As is usually the the conductor insulated with the composition of Example case, it was necessary to run the wire successively through shows a clear advantage in hours to failure over the the enamel bath and baking oven several times at a coripoiyvinyl formal resin insulation and is indicative of the stant speed in order to provide the total insulation desired. superiority ot the compositions of the invention in this Solvent resistance is determined by immersing the property. Heat-aging data was not obtained on the coated wires in a mixture of equal parts of toluene and '20 enamel containing the polymethylol phenol since the ethanol and a 70/ 30 mixture of toluene and ethanol for enamel was unsatisfactory in solvent resistance and approximately ten minutes and observing the eiects of ilexibility. The enamels of the invention are obviously the mixed solvents. In the heat shock test, the conductor superior to those containing polymethylol phenols in is wound on a mandrel equal to or greater than its ditiexibility, solvent resistance, and heat shock properties. ameter, and placed in an oven for a period of time. If What i claim as new and desire to secure by Letters the enamel is suitable as wire insulation, it will expand Patent of the United States is: at the same rate that the copper expands, and will adhere l. Ari insulated electrical conductor in which the inuniformly to the copper. It it is an unsatisfactory insu- Salat-ion comprises a hard, exible, tough, abrasion-relating material, it rapidly becomes embrittled and flakes sistant and solvent-resistant coating, said coating being oif. Elongation and flexibility are determined by windthe heat-treated product of a mixture of (l) from about ing conductors or wires around a mandrel equal to or 0.1 to about 7%, by weight of the mixture, of com.- greater than its diameter, after it has been stretched for pounds corresponding to the general formula a certain degree. For example, as indicated in the table, 0 Z CH CHZ elongation and flexibility were determined on wire as it came out of the oven, after it had been stretched approxi- /O mately 10% of its length, 20% of its length, and 30% of its length. In both the heatshock, and the elongation (RH) (Cmom and exibility tests, it will be obvious that the most R, R

severe tests were those in which a mandrel equal to the diameter of the wire wasr employed since the wire is wherein Z is an alkylene radical, R1 R3 and R 1 am Pfaticany Wound around itself- TM abrasion. l'esistalcek radicals selected from the class consisting of hydrogen, was determined by employing a General Electric abrasion halogen, alkyl, aryl and araikyl, and n is a whole num. tester using a 750-gram load, which is the weight used 1n ber equal to from 1 to 3, (2) from about 10 to about the standard abrasion test for polyvinyl formal enamelS. 17%, by weight of the composition, of a complex epoxide In the fOllOWing tabl@ IISUROIIS (2), (3) and (4) 4 resin containing epoxy groups and comprising a polycorrespond to the compositions of Examples 2, 3 and 4, ether derivative of a polyhydric organic compound serespectively. The diameters of the mandrels employed lected from the class consisting of polyhydric alcohols are indicated as 1X, 2X and 3X, meaning respectively l, and phenols containing at least two phenolic hydroxy 2 and 3 times the diameter of the wire tested. groups, (3) from about 7 to about 15%, by weight of /ff Poiy- Polyliisulatioii vinyl (2) (3) (4) vinyl (2) (3) (4) Formal Formal Tem rature C.) 300 300 300 300 300 300 300 300 wirelsepeeaio/(min.) i6 16 1e is 2o 2o 20 zo Solveliiorl' E E E F E E E F vo/ao E E E F E E E F Hmaiisriil E E E E n u E E ix E E E E E E E E Elongation and Fle bil E E E E E E E E giga??? E E E E E E E E 2X. E E E v E E E E. E E E E E .is E E E 2X-. E E E E E E E E 1X E s a s e a s s h E 30sg/T?? E E E F E E E E 2X E E E F E E E E 1X E E E F E E E F 30%str E E E E E E E E 3X E E E F E E E E 2X E E E F F, E E E ix T E E F F E E F F i 750 m. usjiiron. r e s i.; i 7a 5 7 155 auA 79 55 im Heatag 84 84 63 84 84 E s-Exoellent. F Faiied.

the mixture, of the condensation reaction product of urea and formaldehyde, and (4) from about 60 to about 80%, by Weight of the mixture, of an organic solvent.

2. An insulated electrical conductor in which the insulation comprises a hard, exible, tough, abrasion-resistant and solvent-resistant coating, said coating being the heattreated product of the mixture of (1) from about 0.1 to about 7%, by weight of the mixture, of a product of reaction of an epihalogenohydrin with a mixture of ingredients containing as essential materials the three metal methylol phenates having the formulae:

(a) OM CHzOH (b) OM CHzOH CHzOH and (c) i (INM HO CH2- CHaOH CHzOH Where M is selected from the group consisting of sodium, potassium and barium, (2) from about 10 to about 17%, by weight of the mixture, of a complex epoxide resin containing epoxy groups and comprising a polyether derivative of a polyhydric organic compound selected from the class consisting of polyhydric alcohols and phenols containing at least two phenolic hydroxy groups, (3) from about 7 to about 15%, by weight of the mixture, of the condensation reaction product of urea and formaldehyde and (4) from about 60 to about 80%, by weight of the mixture, of an organic solvent.

3. An insulatedl electrical conductor in which the insulating comprises a hard, tiexible, tough, abrasionresistant and solvent-resistani. coating, said coating being the heat-treated product of a mixture of 1) from about l to about 4%, by weight of the mixture, of the product oi reaction of epichlorohydrin with a mixture of ingredients containing as essential materials the three sodium methyloi phenates having the formulae:

(a) (|)Na CHzOH (b) om CHQOH CHQOH and (c) (|)Na HO CH2- CHaOH CHzOH References Cited in the iile of this patent UNITED STATES PATENTS Greenlee Oct. 31, 1950 Martin Nov. 17, 1953 

1. AND INSULATED ELECTRICAL CONDUCTOR IN WHICH THE INSULATION COMPRISES A HARD, FLEXIBLE, TOUGH, ABRASIN-RESISTANT AND SOLVENT-RESISTANT CATING, SAID COATING BEING THE HEAT-TREATED PRODUCT OF A MIXTURE OF (1) FROM ABOUT 0.1 TO ABOUT 7%, BY WEIGHT OF THE MIXTURE, OF COMPOUNDS CORRESPONDING TO THE GENERAL FORMULA 